The long-running debate over the origins of covid-19 took another twist this week, after a French scientist spotted that genetic sequences databased by Chinese researchers suggest the coronavirus responsible may have come from animals such as raccoon dogs at the Huanan Seafood Market in Wuhan.
Within days, the footage was deleted by the same researchers – although other scientists managed to upload it beforehand and are continuing their research.
“It is really essential that all the data relating to how this pandemic started is made available immediately,” Marie Van Kerkhove to the World Health Organization (WHO) during a press conference on March 17.
“There are several hypotheses that need to be examined, including how the virus entered the human population, either from a bat, via an intermediate host or via a biosecurity breach in a laboratory. And we don’t have a definitive answer.
Huanan market has long been considered a probable origin of SARS-CoV-2 coronavirusas many of the first cases of covid-19, in December 2019, were in people linked to it and the stalls were selling a range of live and dead animals, not just seafood.
The original host of SARS-CoV-2 is believed to be bats, as they carry many coronaviruses, although they have not yet been found with SARS-CoV-2. The ancestor of this virus may have passed from bats to an intermediate host sold in the market and then to humans.
Another explanation is that the virus escaped from the Wuhan Institute of Virology, where researchers were known to study bat coronaviruses, but not SARS-CoV-2. Although this is an idea less popular with scientists, in February the US Department of Energy declared it to be the most likely explanationbut did not publish supporting evidence.
Now, genetic sequences uploaded to a global virology database called GISAID by the Chinese Center for Disease Control and Prevention may have provided insight into the origin of SARS-CoV-2. These sequences were derived from swabs taken from various surfaces of the market in early 2020 after it closed.
They were noticed by Florence Debarre at the French National Center for Scientific Research, which shared its findings with the WHO on March 14. “I was focusing on market sequences when I logged on, but I didn’t expect to find the data I did find,” says Débarre.
Débarre declined to say more until his analysis was complete, but Van Kerkhove said at the press conference: “Among the samples positive for SARS-CoV-2, they saw evidence of Animal DNA Some of these animals include raccoon dogs.
Raccoon dogs (Procyonoid nyctereutes) have already been shown to be susceptible to SARS-CoV-2 and able to spread it. “We know they’re good at wearing it,” says Alice Hughes at the University of Hong Kong.
This does not prove that raccoon dogs or any of the other animals in the market were infected with the virus in December 2019 and such evidence is now impossible to find, says Hughes.
Jonathan Stoye of the Francis Crick Institute in London says: “The data appears to provide compelling evidence that raccoon dogs and other animals were on the market at a critical time. This is another link in the chain that you would expect to see if the pandemic started out this way.
In view of the information shared by Débarre, Van Kerkhove said that the WHO had asked the Chinese Center for Disease Control and Prevention to republish the genetic data. “The big problem is that this data exists and it is not easily accessible to the international community, not to mention that it should have been made available years earlier.”